[bug #21401] Newline inserted by grep at EOF causes false positives

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?21401>

                 Summary: Newline inserted by grep at EOF causes false
positives
                 Project: grep
            Submitted by: None
            Submitted on: Tuesday 10/23/2007 at 13:57 UTC
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:


I have the following file:

Line 1\r\n
Line 2

The first line has a DOS newline, while the second has no newline at all.

For information, the hexdump of the file is:
00000000  4c 69 6e 65 20 31 0d 0a  4c 69 6e 65 20 32
0000000e


I want to know if the file contains Unix newlines (\n).
Therefore, I run grep on it in the following way:

$ grep -P '[^\x0d]\x0a' file.txt
Line 2

The problem is that grep thinks that Line 2 matches, which is definitely not
the case.

The following experience pinpoints the problem:

$ grep -P '[^\x0d]\x0a' file.txt | hexdump -C
00000000  4c 69 6e 65 20 32 0a
00000007

grep has apparently inserted a newline automatically at the end of the file,
using the Unix format, which then matches my regexp.

So grep should find not match in the file, and it finds one.
It's a corner case, but it's an bug, even an annoying bug if one is
troubleshooting newline issues.






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